In the application of paints and lacquers to automobile bodies and other types of articles it is customary to carry out such operations in enclosed spray booths and to introduce into such spray booths a curtain of water to wash the air and to remove over-sprayed paints or lacquer solids. The water containing suspended solids is filtered or otherwise treated to separate the solids so that the water can be recycled.
This process involves many problems. Thus, the paint and lacquer solids are normally tacky and tend to adhere to the walls, ceilings and floors of the spray booths which makes it necessary to shut down the operation from time to time in order to clean the spray booths. The deposits which are formed on the walls, ceilings and floors of the spray booths are also subject to the growth of anaerobic corrosive bacteria (e.g., desulfovibrio) which generates corrosive and highly objectionable hydrogen sulfide.
The paint and lacquer solids which are washed away and form suspensions in the water that is removed from the spray booths present a disposal problem. In order to avoid contamination of the environment it is customary to separate these solids from the water and to recirculate the water but these solids are difficult to separate by the usual method of filtration.
It is therefore desirable to control pollution and contamination in paint or lacquer spray booths so as to prevent, as much as possible, the deposition of paint and lacquer solids on walls, ceilings and floors and to condition the sludge which is removed with the water so that it can be readily filtered and the water which forms the filtrate can be returned for use in the process.